1. Field of the Invention
The present invention relates to a medical device for measuring spatial relationships between anatomical structures. More specifically, the present invention relates to a surgical instrument for measuring an intervertebral space in a precise manner so as to allow for optimal restoration of a damaged area.
2. Description of the Related Art
In prosthetics for intervertebral disks, it is customary to use so-called intervertebral prostheses as disk replacements. Such intervertebral prostheses are inserted between the vertebral bodies as part of an operation, replacing the defective disks removed earlier. To ensure that the original mobility and function of the spinal column is optimally restored, it is necessary that the damaged intervertebral space be reconstructed with optimal precision, and that the dimensions and positioning of an intervertebral prosthesis be chosen in optimal fashion. As a rule, intervertebral prostheses of the type mentioned consist of two prosthetic plates, each connected with a vertebral body. In some versions, between the prosthetic plates, a prosthesis core is placed, on which the prosthesis plates glide and assume the damping function of the removed disk. In determining the dimensions for an intervertebral prosthesis to be inserted, especially the area of the prosthetic plates, the overall height of the intervertebral prosthesis and an angular setting of the surfaces of the prosthetic plates facing the vertebral bodies to each other are decisive.
The related arts teach that the measurements of the intervertebral prosthesis are taken preoperatively using X ray or CAT imagery, and during the operation are verified after removal of the disk by test use of implants. Implant measurements are verified by inserting a test implant between the vertebral bodies mechanically spread apart from each other; the spreading is released; and then, using an X ray image, the register form of the implant is checked.
What is not appreciated by the prior art is that it is necessary to spread the vertebral bodies multiple times to remove and re-insert the test prostheses for insertion and checking of the intervertebral prostheses. On the one hand, this takes up a large part of the time for surgery; and, on the other hand, it necessitates unnecessary mechanical loads on the patient's spinal column.
Accordingly, the inventors recognize a need for an improved surgical instrument for measuring an intervertebral space in a precise manner so as to allow for optimal restoration of a damaged area